Methods of controlling jacket bonding with cable armor and water blocking at strength members

ABSTRACT

An armored cable having a polymer covering where the bond between the armor and the covering is controlled by introducing particulate matter at the interface of the armor and covering. A filler material is applied to the exterior surfaces of the cable strength elements in order to inhibit the formation of voids in the polymer covering that would otherwise promote water migration along the cable.

RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application No. 61/377,585, filed Aug. 27, 2010, thecontent of which is relied upon and incorporated herein by reference inits entirety.

RELATED APPLICATIONS

This application is related to U.S. application Ser. No. 12/214,461,filed Jun. 19, 2008 and entitled “FIBER OPTIC CABLE HAVING ARMOR WITHEASY ACCESS FEATURES”, U.S. application Ser. No. 12/150,656, filed Apr.30, 2008 and entitled “FIBER OPTIC CABLE AND METHOD OF MANUFACTURING THESAME”, U.S. App. No. 61/118,196, filed Nov. 26, 2008 and entitled“METHODS OF CONTROLLING BONDING AND ARTICLES FORMED THEREFROM”, U.S.App. No. 61/139,187, filed Dec. 19, 2008 and entitled “METHODS OFCONTROLLING BONDING AND WATER BLOCKING IN CABLES”, InternationalApplication PCT/US09/65760, filed Nov. 24, 2009 and entitled “METHODS OFCONTROLLING BONDING AND ARTICLES FORMED THEREFROM”, and U.S. App. No.61/121,711, filed Dec. 11, 2008 and entitled “CABLE JACKET WITH VARIABLEPERIMETER BOND”, the entire contents of these applications being herebyincorporated by reference as if presented herein.

SUMMARY

According to a first embodiment, an armored fiber optic cable comprisesa fiber optic cable core including at least one optical fiber capable ofconveying optical signals, armor at least partially enclosing the core,particulate matter disposed on an exterior surface of the armor, atleast one strength element adjacent to the armor, and a covering overthe armor and the particulate matter and at least partially embeddingthe at least one strength element, wherein filler material covers atleast a portion of an exterior of the at least one strength element. Thefiller material is of different composition than the covering, and islocated between the strength element and the fiber optic cable armor toinhibit the formation of voids or channels adjacent to the armor throughwhich water could migrate.

According to one aspect, a method of making an armored fiber optic cablecomprises providing a fiber optic cable core including at least oneoptical fiber capable of conveying optical signals, at least partiallyenclosing the fiber optic cable core in armor, applying particulatematter to an exterior surface of the armor, providing at least onestrength element, applying filler material to the exterior of thestrength element, and, after applying the particulate matter, forming acovering over the armor. The at least one strength element is adjacentto the exterior surface of the armor and at least partially embedded inthe covering, and the at least one strength element is adjacent to theexterior surface of the armor and at least partially embedded in thecovering.

Those skilled in the art will appreciate the above stated advantages andother advantages and benefits of various additional embodiments readingthe following detailed description of the embodiments with reference tothe below-listed drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

According to common practice, the various features of the drawingsdiscussed below are not necessarily drawn to scale. Dimensions ofvarious elements in the drawings may be expanded or reduced to moreclearly illustrate the embodiments of the invention.

FIG. 1 is a partial cutaway view of a cable according to a firstembodiment with a portion of the cable covering pulled away from thecable armor.

FIG. 2 is a section view of the armored cable of FIG. 1 taken along line2-2 in FIG. 1.

FIG. 3 is a longitudinal section view of the interface of the armor andcovering of the cable of FIG. 1.

FIG. 4 is a longitudinal section view of armor.

FIG. 5 is a schematic illustration of a manufacturing line suitable forforming cables with controlled bonding between surfaces in the cables.

FIG. 6 is an isolated section view of a portion of a cross section of acable according to an alternative embodiment.

FIG. 7 is an isolated section view of a portion of a cross section of acable according to yet another alternative embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments,examples of which are illustrated in the accompanying drawings. Wheneverpossible, the same reference numerals will be used throughout thedrawings to refer to the same or like parts.

FIG. 1 is a partial cutaway view of a cable 100 according to a firstembodiment. FIG. 2 is a section view of the cable taken on line 2-2 inFIG. 1. Referring to FIGS. 1 and 2, the cable 100 generally comprises acore 110, armor 120 having an overlap 121 and an exterior, abuttingsurface 122, and a covering 130 surrounding the armor 120 and having aninterior, abutting surface 134 in contact with the surface 122 of thearmor 120. One or more elongate strength elements 140, such as a pair ofstrength elements 140 on either side of the core, extend along thelength of the cable. The core 110 includes a polymeric buffer tube 150and a dry insert 154 disposed within the interior of the armor 120 andextending along the length of the cable 100. A second dry insert (notillustrated) can be located between the exterior of the buffer tube 150and the armor 120.

In the exemplary embodiment, the core 110 also includes one or moreoptical fibers, each optical fiber having the ability to convey fiberoptic communications. The exemplary core 110 can therefore be referredto as a “fiber optic cable core”. In the illustrated embodiment, theoptical fibers 112 are arranged as a stack 114 of a plurality of opticalfiber ribbons 116, each optical fiber ribbon 116 having a row of twelveoptical fibers 112 encased in a common ribbon matrix 118. Otherarrangements of optical fibers are possible. The dry insert 154 can be,for example, a longitudinally extending foam, felt, cloth, etc. tape. Ifdesired, the buffer tube 150 and dry insert(s) can be omitted to provideease of access to the ribbon stack 114.

The armor 120 surrounds and protects the core 110 and has a generallytubular shape. The interior of the armor 120 can abut an exteriorsurface of the core 110, or an intervening dry insert (not shown) may bepresent between the armor and core. In this specification, the term“armor” does not necessarily indicate a metallic element, and allows forthe use of dielectric armors, for example. The armor 120 can include acoating 124 comprising a polymer layer formed over a base armor material126, the coating 124 serving as the abutting surface 122 of the armor.Alternative and/or additional layers may also be included in the armor120, so that the armor 120 is actually an armor laminate. The term“armor” is used in this specification for simplicity of description andis intended to encompass armor laminates as are generally known in theart. The structure of an exemplary armor is discussed in detail belowwith reference to FIG. 4.

Still referring to FIGS. 1 and 2, the covering 130 surrounds and tightlyabuts the armor 120 and can be referred to as a “jacket” or “cablejacket.” In the exemplary embodiment, the covering 130 is a polymermaterial formed over the armor 120 by an extrusion process. The polymerused to form the covering 130 can be materials such as, for example,plastics. In the exemplary embodiment, the polymer covering 130 isUV-resistant medium density polyethylene (MDPE). The covering 130 can begenerally described as comprising a polymer or as “polymeric”, butamounts of other non-polymers can be included in the covering. In thisspecification, the term “polymeric” allows for the inclusion ofadditives, and indicates that the covering comprises at least 60% or atleast 70% of one or more polymer materials.

Still referring to FIGS. 1 and 2, bonding of the abutting surface 134 ofthe covering 130 to the armor 120 is controlled using a full or partialapplication of particulate matter 170 at the interface of the covering130 and the armor 120. The particulate matter 170 and armor coating 124may be relatively small and are not visible in FIG. 2. The particulatematter 170 is shown in more detail in FIG. 3 and the armor 120 is shownin more detail in FIG. 4. For the purposes of this specification, thecoating 124 on the armor 120, if present, is considered to be part ofthe armor because armor suppliers often pre-coat the bulk materials usedto form such armors before shipping. Polyethylene is a common coatingmaterial. Polypropylene is another coating material. If a typicalplastic cable jacket material (e.g. MDPE) were extruded directly onto anpolyethylene armor coating, a strong thermoplastic bond would be formedbetween the armor coating and the resultant plastic covering. Thebond-controlling particulate matter 170 according to the presentinvention is applied at the interface of the armor 120 and the covering130 in order to interrupt and/or weaken the thermoplastic bonding, andthereby facilitate separation of all or a part of the covering 130 fromthe armor 120 (shown in FIG. 1).

An adherent material layer 174 can be located at the interface of thecovering 130 and the armor 120. The adherent 174 can be, for example, alayer formed from a viscous liquid applied to the armor 120 duringmanufacture of the cable 110. The adherent 174 helps the particulatematter 170 to adhere to the armor 120 exterior surface before thecovering 130 is formed over the armor. The adherent material 174 can bea liquid, such as a liquid of medium viscosity. In the exemplaryembodiment, the adherent material 174 is an oil. While the adherentmaterial 174 is illustrated on the surface of the armor 120 in FIG. 1,materials such as oils will likely be wholly or substantiallyincorporated into the covering 130 during extrusion of the covering.

The particulate matter 170 can be comprised of a plurality of individualinorganic or organic particles distributed over all or a part of thesurface 122 of the armor 120. The density and arrangement of theparticulate matter 170 can be selected to provide a desired degree ofbonding between the covering 130 and the armor 120. Suitable inorganicparticulates include mineral particulates such as Talc-HydratedMagnesium Silicate (Talc), clay (e.g., hydrated aluminum silicate), andsuperabsorbent polymers (SAP) such as are used in fiber optic cablewater-blocking applications. An example of a suitable mineralparticulate is VANTALC 2500® available from R.T. Vanderbilt Company,Inc. Another suitable particulate is a crosslinked sodium polyacrylatesold under the trade name CABLOC GR-211, available from Evonik, Inc. ofGreensboro N.C. Either talc or clay could be mixed with a smallpercentage of highly hydrophilic SAP particulates to providewater-blocking properties. Corrosion-resistant absorbent powders can beused as a portion of or may comprise all of the bond-controllingparticulate matter.

Other than in the vicinity of the strength elements 140, the interfaceof the covering 130 and the armor 120 can be free of materials such asglues and other materials commonly used as release layers, and theabutting surface 134 of the covering 130 directly contacts the surface122 of the armor 120 except where the particulate matter 170 (and thethin layer of adherent material 174, if present) is interposed betweenthe armor 120 and the covering 130. The term “abutting” as used herein,accordingly indicates adjacent surfaces of armor and covering layer,allowing for the intervening presence of particulate matter and adherentmaterial, and where the coating 124 is considered to be a part of thearmor 120. In the illustrated embodiment, the particulate matter 170 isgenerally dispersed over the entire surface area of the armor 120,although not necessarily uniformly so. In this specification, when apercentage of a surface or element is described as an application ortarget area of a surface for application of particulate matter, thepercentage refers to a region of the armor surface over whichparticulate matter is applied to the surface, and not to the totalsurface area of the surface area actually occupied by particulate.

During extrusion of the covering 130 over the armor 120, alongitudinally extending void or channel would ordinarily form between astrength element 140 and the armor 120. The longitudinally extendingvoids would present paths for water propagation along the length of thecable 100. According to one aspect of the present embodiments, a fillermaterial 190 is applied to the strength elements 140 before the coveringis applied over the armor 120. The filler material 190 can be, forexample, a viscous, semi-solid material applied to the surface of thestrength elements 140 that is of different material composition than thecovering 130. The filler material 190 can be applied over the entiresurface of the strength elements 140, as shown in FIGS. 1 and 2.Alternatively, selected portions of the strength elements 140, inparticular the portions of the strength element surfaces 140 facing theconvex exterior of the armor 120, can have filler material 190 appliedthereto.

The filler material 190 is applied to the strength elements 140 insufficient amounts such that it contacts the surface of the armor 120and leaves little or no perceptible voids or channels in the covering130, so that no significant paths for water migration are created in thecovering 130. The filler material 190 can cover a length of the surface122 of the armor 120, when seen in cross section, that is at least 40%of a major dimension of the strength element cross section—which is astrength element diameter in the exemplary embodiment. Referring to FIG.2, the exemplary filler material 190 covers a length of the armorsurface 122 that is greater than 100% of the strength element diameter.A ripcord 196 can be included adjacent to one or both strength members140 to allow the covering 130 to be more easily removed during cableaccess. In FIG. 2, the ripcord 196 is enclosed within the fillermaterial 190.

The filler material 190 can be materials such as thermoplastics,elastomerics, and adhesives. In general the filler material 190 has alower melt temperature than the jacket extrudate material. Duringextrusion of the filler material, the molten filler material viscosityis significantly lower than that of the extrudate; the melt flow indexof the filler material is accordingly higher than that of the extrudate.The lower viscosity allows the filler material to flow freely and fillany voids in the vicinity of the strength elements during extrusion. Bycontrast, higher viscosity jacket covering materials are less likely tofully flow into the areas between the armor and strength member, unlessthe line speed is reduced, which also reduces manufacturing efficiency.After cooling in the finished cable, the cohesive strength of the fillermaterial 190 is substantially less than the strength of the covering 130and the armor laminate materials. The relatively low cohesive strengthof the filler material allows separation of the covering 130 duringaccess procedures. According to one aspect, the filler material 190 canbe a material of molecular weight of 2500 g/mol or more that is appliedas a liquid after heating. The molecular weight of the filler isrelatively low when compared to the covering 130, however. For example,the filler material may have a molecular weight in the range of2,500-5,000 g/mol, while the covering material may be in the range of5,000-100,000 g/mol. In general, the covering material will have amolecular weight that is at least 10% greater than that of the fillermaterial. In another embodiment, the covering material molecular weightis at least 50% greater than the filler material. The filler materialmay be relatively stable and not vaporific until heated to 250° C. Onefiller material 190 is VERSA-WELD™ 34-262 Hot Melt Adhesive availablefrom Henkel Corporation, Bridgewater, N.J.

FIG. 3 schematically illustrates the controlled bonding mechanismprovided by the introduction of the particulate matter 170. The sectionin FIG. 3 can be described as a schematic representation of a highlymagnified longitudinal section of a small portion of the interface ofthe covering 130 and the armor 120, particularly at the coating 124 ofthe armor. In conventional jacket covering applications, an intermediatelayer of glue or other adhesive is applied to the entire armor exteriorbefore extruding a polymer jacket over the armor. In order to access thecable interior in conventional cables, the jacket is separated from thearmor at the armor-adhesive-jacket interface, which typically has a highbonding force. According to one aspect of the present embodiment, asschematically represented in FIG. 3, the individual particles 176 of theparticulate material 170 interrupt the bonding at the interface of thecovering 130 with the armor 120. In FIG. 3, a section of the interfaceis shown as the bond of the coating 124 of the armor 120 with thecovering 130. The covering 130, which is heated to a fully or partiallymolten state during application over the armor 120, may form a strongthermoplastic bond with the material of the armor coating 124, which canbe a polymer such as polyethylene. The particulate material 170interrupts the interlayer bond between the coating 124 and the covering130 at a plurality of locations. Each particle 176 (which can be formedfrom an agglomeration of particles) therefore provides an area where thearmor/covering bond can fail relatively easily during separation of thecovering 130 from the armor 120. Failure at the armor/particle/coveringinterfacial locations can be generally referred to as “cohesive failure”because the individual particles 176 or an agglomeration of particles176 can fail internally (i.e., the particle or agglomeration ofparticles breaks into separate pieces) to facilitate separation. Theindividual particles 176 break or undergo cohesive failure as thecovering 130 is separated from the armor 120. The failure at theparticulate material 170 can also be “adhesive” in that the bond of theparticulate matter 170 with the covering 130 and/or with the armor 120can be relatively low. In FIG. 3, the particles 176 are illustrated asspherical for simplicity of illustration. In practice, the particulatematter can have any shape. As shown in FIG. 3, the individual particles176 may become at least partially embedded in the covering 130 duringextrusion. The particles 176 may also become at least partially embeddedin the armor coating 124.

FIG. 4 is a partially schematic longitudinal section view of a portionof the armor 120 used in the cable of FIG. 1. The armor 120 can includea base armor material layer 126 with the coating 124 adhered to the basearmor 126 by an adhesive layer 128. The adhesive layer 128 can be, forexample, a film of an adhesive such as ethylene acrylic acetate (EAA)copolymer. The coating 124 can include additional layers, and can, forexample, be a laminate of multiple films. The base armor material layer126 can include materials such as metals, dielectrics, etc. In theillustrated embodiments, the base armor 126 is metallic and the coatingis a polyolefin.

FIG. 5 illustrates a manufacturing line 500 for forming the cable 100having controlled bonding of the covering 130 to armor illustrated inFIGS. 1-3. Referring to FIG. 5, a flat sheet 502 of armor material, acore 504, and one or more strength elements 506 are continuouslyprovided generally along the process direction 508. The flat sheet 502can be a coated metallic, for example, and will ultimately form thecable armor 120. The sheet 502 can include a base armor material coveredon one side with a polymer coating adhered by adhesive (e.g., asillustrated in FIG. 4) that forms the armor coating 124. The flat sheet502 can be paid off from a roll, for example. The core 504 can be anylongitudinally extending element that is to be enclosed within an armorand a covering. In the illustrated embodiment, the core 504 is a fiberoptic cable core 110 as shown in FIG. 2 including one or more opticalfibers and paid off of a spool. In the exemplary embodiment, thestrength elements 506 are elongate wire metallic elements of circularcross-section paid off of a spool.

Still referring to FIG. 5, the flat armor sheet 502 is advanced throughan applicator 510 where a coating of adherent material is applied to thesurface of the flat sheet 502 that becomes the abutting surface 122(FIG. 1). The adherent can be a liquid such as an oil, and can beapplied to the surface of the sheet 502 by a rotating roller that issaturated in the adherent.

The coated sheet 512 then advances into a corrugator 520 that corrugatesthe sheet 512. The corrugator 520 can be a conventional device, such asa device having two counter-rotating corrugating rollers between whichthe sheet 512 passes.

The corrugated sheet 522 is advanced into an armor former 530 that formsthe armor sheet 512 into a general tube configuration around the core504 so that it has the configuration shown in FIG. 1. The armor former530 can be of a conventional configuration, and can include a die ofdecreasing diameter that continuously concentrically compresses andwraps the armor sheet into a tubular form about the cable core 504. Thecore 504 is disposed in the interior of the armor tube, with theadherent-coated surface of the armor facing outward.

If desired, the combined armor/core assembly 532 can be advanced throughan adherent smoother (not illustrated) that smooths out the adherent onthe exterior peripheral surface of the corrugated armor of the assembly532. One or more high velocity gas jets, for example, can be used tospray air over the adherent to distribute the adherent over the surfaceof the sheet 522. Brushes may be used alternatively or in addition togas jets.

The combined armor/core assembly 532 then advances through a particulateapplicator 550. The particulate applicator 550 deposits particulatematter onto the surface of the armor tube of the armor/core assembly532. The adherent coating on the armor of the armor/core assembly 532helps the particulate matter to adhere to the surface of the armor/coreassembly. The particulate applicator 550 can be a generally enclosedlongitudinal cabinet or other structure through which the armor/coreassembly 532 travels. Particulate matter can be introduced into theinterior of the particulate applicator 550 by gravity, pressurized air,etc. For a general application of particulate over the entire surface ofthe armor, one or more air nozzles can be in communication with theapplicator interior to create swirling or other flow patterns todistribute the particulate matter over the armor/core assembly 532.Alternatively, relatively small nozzles can be used to direct streams ofparticulate matter targeted to specific application or target areas ofthe surface of the armor/core assembly 532. Particulate matter can alsobe applied to the armor surface by passing the armor through a chamberthat is in communication with a hollow cylindrical drum (notillustrated). Pressurized gas such as atmospheric air is introduced intothe drum so as to create a vortex flow within the drum. An aperture isformed in the drum exterior that is in communication with a supply ofparticulate matter. The vortex flow creates a partial vacuum that drawsin the particulate matter, with the particulate matter mixing in thevortex flow. Centripetal acceleration will cause the particulate matterto circulate at or near the outer periphery of the hollow drum, so thechamber through which the armor passes can be at the outer perimeter ofthe drum so that the particulate matter has a high chance of impingingon the armor and adhering thereto. In order to more effectivelydistribute particulate matter over the armor, drums can be arrangedsequentially along the manufacturing line so that each drum can directparticulate matter towards a particular section (or arc section) of thearmor perimeter. For example, four drums can be arranged sequentially onthe manufacturing line, the drums being arranged at 0, 90, 180 and 270degrees about the armor for targeting separate quadrants of the armorexterior. Alternatively, particulate matter can be simply dropped orgravity-fed over the armor.

The strength elements 506 are advanced through a flooding head 570 wherethe strength elements are wholly or partially immersed by fillermaterial deposited over the elements 506. The entire exterior surfacesof the strength elements 506 can be targeted for coating by the fillermaterial, or selected regions, such as the regions facing the exteriorof the armor, can be covered with filler material. The armor/coreassembly 532 can travel through the flooding head 560 with the strengthelements 506, and can pass through an enclosed tube so that it is notcovered in filler material. Ripcords (not shown), if present, can beadvanced into the flooding head 560 in parallel with the strengthelements 506. In one embodiment, the filler material is supplied to theflooding head at a rate of 0.1 to 1.0 kg per cable kilometer perstrength element.

The armor/core assembly 552 with applied particulate matter, and thecoated strength elements 506, are advanced to an extrusion apparatus570. The extrusion apparatus 570 works according to conventionalprinciples, in which the armor/core assembly 552 is advanced through anextrusion die where extrudate is introduced around the assembly 552. Themolten extrudate forms an extrusion cone around the assembly 552 thateventually shrinks radially or draws down and tightly forms onto theexterior surface of the armor of the assembly 552. Alternatively, theextrudate can be introduced under pressure directly onto the exteriorsurface of the armor assembly 552 as it passes through the extrusionapparatus 570 and as the extrusion die defines the exterior profile ofthe jacket. The extrudate forms the tubular covering 130 illustrated inFIG. 1. During extrusion, the filler material coating the strengthelements contacts and fills voids in the extrudate between the strengthelements 506 and the armor of the assembly 552. The assembly can then beadvanced through a cooling device such as a trough, the cooled assemblynow constituting the cable 100 (FIG. 1). After cooling, the fillermaterial can be bonded to the armor and to the strength element. Thecable 100 can then be collected on a take-up device, such as, forexample, a take-reel or take-up coiler. As an alternative to coating thestrength elements 506 with filler material prior to entering theextrusion head, the filler material can be applied in the extrusionhead. The filler material could also be applied directly to the surfaceof the armor as opposed to the strength members. In this embodiment, thefiller material can be applied to the armor adjacent to the strengthmembers but not at other locations of the armor.

The strength elements 506 and filler material can become wholly orpartially encased in the covering 130, as shown in the embodiment ofFIG. 2. The strength elements 506 can be aligned so that they areclosely adjacent to or abut the exterior surface of the armor/coreassembly at one or more locations, with the filler material preventingthe formation of voids or channels between the strength elements and thearmor. Upstream of the extrusion tooling, the strength elements can bespaced from the armor. Without being bound by theory, Applicants believethat excessive impacts of the strength elements with the armor duringprocessing may cause the overlap point 121 to rotate (e.g., rotate so asto deviate from a nominal clock location in FIG. 2) excessively duringmanufacture.

FIG. 6 is a detailed section view of a portion of a transversecross-section of a cable 600 according to another embodiment. The cable600 can be substantially identical to the cable 100 shown in FIGS. 1 and2, except for the application of filler material to the strengthelements. In FIG. 6, the filler material 690 is selectively applied tothe surface of the strength elements 140 that faces the convex surfaceof the armor 120, and is not intentionally applied to the outwardlyfacing surfaces of the strength elements 140. The ripcords 696 may beoutside of the filler material 690, and disposed within the material ofthe covering 130.

FIG. 7 is a detailed section view of a cable 700 according to anotherembodiment. The cable 700 can be substantially identical to the cable100 shown in FIGS. 1 and 2, except for the application of fillermaterial to the strength elements. The ripcords 796 may be outside ofthe filler material 790, and disposed within the material of thecovering 130.

In the illustrated embodiments, the strength elements 140 may be alignedso that they abut, at least intermittently, the corrugated armor 120, orso that the strength elements 140 are very closely spaced with the armor120. The filler material is intended to fill the area between thestrength elements and the core sufficiently to inhibit water migrationalong the cables, although small voids or channels may be present.

In the illustrated embodiments, the flow rate of particulate matter tothe particulate applicator 550, and accordingly the total amount ofparticulate matter incorporated into the cable, can be varied in orderto obtain a desired bond strength at the interface of the covering 130and the armor 120. In general, the total amount of particulate matterincorporated in a cable will be at least 25 milligrams per meter incables having diameters in the range of 5 mm to 35 mm Higher amounts,such as at least 500 mg/m, or even over 2000 mg/m of cable can be usedin cables having diameters in the range of 5 mm to 35 mm. For cableshaving a diameter of 10 mm or more, amounts over 100 mg/m, or over 1000mg/m or over 2000 mg/m can be used.

Example 1

A fiber optic cable 100 as illustrated in FIG. 1 has an MDPE plasticcovering 130 extruded over an armor 120 or metallic base material 126and having a polyethylene coating 124. The particulate matter 170 is amineral particulate and is applied generally over an application areathat is essentially all of the armor exterior surface. The particulatedoes not cover all of the surface area, and occupies about half of thearea of interface of the armor coating 124 and the MDPE covering 130.For a 100 mm² area of interface between the armor coating 124 and thecovering 130, 50 mm² of the interface area has an interlayer failuremechanism (i.e., thermoplastic bonding of covering to coating) with arelatively high bonding force of 2.0 N/mm². For the other 50 mm² of theinterface area, the presence of particulate matter 170 at the interfacecreates regions of cohesive bonding within the compacted particulateshaving a relatively low bonding force of 1.0 N/mm². For this estimatedexample, the average bonding force for the 100 mm² area of interface is1.5 N/mm². The strength elements 140 are formed of steel metallic wireof 1.5 mm diameter rolled off of a spool. The strength elements 140extend along the length of the cable 100 and at least intermittentlycontact the surface of the corrugated armor 120. Molten filler materialis supplied to a flooding head at a rate in the range of 0.1-1.0 kg percable kilometer for each strength element 140.

According to the present embodiments, the bond between abutting layersor elements can be controlled by a relatively simple application ofparticulate matter between the layers. The particulate matter can bedelivered by a pneumatic delivery system, which is cheaper than the pumpconveyance systems required for adhesives. Further, the bonding forcecan be relatively easily controlled by varying the amount of particulatematter introduced into the particulate applicator 550, the air flowvolumes, patterns and velocities used to mix the particulate matter, theparticle size and composition, and other easily managed variables. Also,there is a large selection of particulate matter available at relativelylow prices. Filler material introduced between the strength elements andthe core exterior prevent or inhibit the formation of channels along thecable that would allow water migration.

Particulates may also be applied to the armor using an electrostaticapplicator. For example, the armor can be maintained at a positivecharge, and the particulate matter can be oppositely charged and appliedto the surface of the armor. This method obviates the need for anadherent.

Particulate matter can also be applied to the surface of the armor bypassing the armor through a fluidized bed of particulate matter.

In this specification, the term “particulate matter” is understood toinclude mixtures of particulates of differing type and/or particle sizeas well as single composition and size particulates.

The optical fibers employed in the present embodiments may be anysuitable type of optical waveguide. Moreover, the optical fibers may bea portion of a fiber optic ribbon, a bundle of optical fibers, or thelike.

Alternative particulates include crosslinked sodium polyacrylateavailable from Absorbent Technologies, Inc. under the tradename AQUAKEEPJ550P, copolymers of acrylate and polyacrylamide, graphite, boron,calcium carbonate powder, and flame retardant powders such as aluminumtrihydroxide (ATH), and/or the like.

The covering 130 can be made from extrudable materials such as, forexample, MDPE, UV-stabilized polyethylenes, etc.

The strength elements 140 in the illustrated embodiments are metallic.Other materials, including dielectrics such as glass-reinforced plastic(GRP) can also be used to form strength elements in accordance with thepresent embodiments.

The core 110 can be fiber optic core types such as stranded tube cables,monotube cables, micromodule cables, slotted core cables, loose fibers,tube assemblies, loose and stranded tube, tight-buffered fiber, singletube drop cables or the like. Additionally, the cable cores can includeany suitable components such as water-blocking or water-swellingcomponents, flame-retardant components such as tapes, coatings, or othersuitable components. Fiber optic cable cores may have any suitable fibercount such as a 6-fiber MIC cable or 24-fiber MIC cable available fromCorning Cable Systems of Hickory, N.C. Suitable specific fiber opticcore cable types include cables sold under the ALTOS® trademark,SST-RIBBON™, and SST-UltraRibbon™ cables available from Corning CableSystems.

What is claimed is:
 1. An armored fiber optic cable, comprising: a fiber optic cable core including at least one optical fiber capable of conveying optical signals; armor at least partially enclosing the core; particulate matter disposed on an exterior surface of the armor; at least one strength element adjacent to the armor; a covering over the armor and the particulate matter and at least partially embedding the at least one strength element; and filler material covering at least a portion of an exterior of the at least one strength element, the filler material being of different composition than the covering, and at least a portion of the filler material being located between the at least one strength element and the armor.
 2. The cable of claim 1, wherein the covering comprises a polymer.
 3. The cable of claim 2, wherein the particulate matter comprises at least one of mineral particulates and hydrophilic particles.
 4. The cable of claim 3, wherein the particulate matter is selected from the group consisting of: superabsorbent polymer, clay, and talc.
 5. The cable of claim 2, wherein at a transverse cross section of the cable, the filler material contacts an exterior of the armor along a length of the armor that is at least 40% of a major cross sectional dimension of the at least one strength element.
 6. The cable of claim 2, wherein the filler material has a lower melt temperature than that of the covering.
 7. The cable of claim 6, wherein the molecular weight of the covering is at least ten percent greater than the molecular weight of the filler material.
 8. The cable of claim 6, wherein the molecular weight of the covering is at least fifty percent greater than the molecular weight of the filler material.
 9. The cable of claim 2, wherein the at least one strength element comprises a first elongate strength element on a first side of the armor and a second elongate strength element on a second side of the armor.
 10. The cable of claim 2, wherein the filler material contacts the armor.
 11. A method of making an armored fiber optic cable, comprising: providing a fiber optic cable core, the fiber optic cable core including at least one optical fiber capable of conveying optical signals; at least partially enclosing the fiber optic cable core in armor; applying particulate matter to an exterior surface of the armor; providing at least one strength element; applying a filler material to the at least one strength element; and after applying the particulate matter, forming a covering over the armor, wherein the at least one strength element is adjacent to the exterior surface of the armor and at least partially embedded in the covering, the filler material contacting the armor.
 12. The method of claim 11, wherein forming a covering over the armor comprises extruding a polymer covering over the armor.
 13. The method of claim 12, wherein applying particulate matter comprises blowing particulate matter onto an exterior surface of the armor.
 14. The method of claim 13, wherein providing at least one strength element comprises providing a first strength element on a first side of the armor and a second strength element on a second side of the armor.
 15. The method of claim 14, wherein at least partially enclosing the fiber optic cable core in armor comprises deforming an armor sheet around the fiber optic cable core.
 16. The method of claim 14, wherein the particulate matter becomes at least partially embedded in the covering during forming of the covering over the armor.
 17. The method of claim 11, wherein applying a filler material to the at least one strength element comprises applying filler material to an exterior surface of the armor adjacent to the at least one strength element. 